Biomedical Engineering Reference
In-Depth Information
that diagnostic imaging techniques have played a decisive role in routine clin-
ical practice in almost all disciplines of contemporary medicine. With further
development of functional imaging techniques, in conjunction with continuing
progress in molecular biology and functional genomics, it is anticipated that we
will be able to visualize and determine the actual molecular errors in a specific
disease within a decade or so, and be able to incorporate this biological infor-
mation into clinical management of that particular group of patients. This is
definitely not achievable with the use of structural imaging techniques.
In this chapter, we will take a quick tour of a functional imaging technique
called
positron emission tomography
(PET), which, in conjunction with
single-
photon emission computed tomography
(SPECT), is commonly known as
emis-
sion computed tomography
. PET is a primer biologic imaging tool, being able
to provide
in vivo
quantitative functional information in most organ systems
of the body. In the following sections, an overview of this imaging technique is
provided, including the basic principles and instrumentation, methods of image
reconstruction from projections, some specific correction factors necessary to
achieve quantitative images, as well as basic assumptions and special require-
ments for quantitation. Paradigms based on the framework of tracer kinetic
modeling for absolute quantification of physiological parameters of interest are
also introduced. However, as they deem inappropriate for inclusion in this topic,
topics on hardware technologies (e.g. display and archival units, data-acquisition
computer system, electronics circuitry, array processors, etc.) of a PET system,
operating principles of a cyclotron, as well as design and development of radio-
pharmaceuticals are not discussed in this chapter.
2.2 A Brief History of PET
The development of PET has involved efforts of investigators from diverse dis-
ciplines and spanned almost the whole twentieth century. At the turn of the
twentieth century, Ernest Rutherford and Frederick Soddy (who coined the
term
isotope
) reported their studies on the nature and cause of radioactivity in
McGill University [6]. Their work on radioactive half-life and exponential de-
cay is the foundation for medical applications of radioisotopes, including the
breakthrough development of emission computed tomography.
